1. Field of the Invention
The present invention relates to a solid-state image-capturing device and an image-capturing device having a plurality of pixels and first and second substrates in which circuit elements constituting the pixels are arranged and which are electrically connected through a connection unit.
2. Description of the Related Art
In recent years, video cameras, electronic still cameras, and the like have been widely popularized. A charge coupled device (CCD)-type or amplification-type solid-state image-capturing device is used for such a camera. The amplification-type solid-state image-capturing device guides signal charges generated and stored by a photoelectric conversion unit of a pixel on which light is incident to an amplification unit in the pixel, and outputs the signal amplified by the amplification unit from the pixel. In the amplification-type solid-state image-capturing device, a plurality of pixels are arranged in a two-dimensional matrix shape. The amplification-type solid-state image-capturing device, for example, includes a complementary metal oxide semiconductor (CMOS)-type solid-state image-capturing device using a CMOS transistor.
Conventionally, a general CMOS-type solid-state image-capturing device adopts a scheme of sequentially reading signal charges generated by photoelectric conversion units of the pixels arranged in a two-dimensional matrix shape for every row. In this scheme, because a timing of exposure in the photoelectric conversion unit of each pixel is determined by the start and end of reading of signal charges, the exposure timing differs for each row. Thus, when an image of an object in fast motion is captured using the CMOS-type solid-state image-capturing device, the object is distorted within the captured image.
In order to eliminate the distortion of the object, a simultaneous image-capturing function (global shutter function) of implementing simultaneity of storage of signal charges has been proposed. In addition, the use of a CMOS-type solid-state image-capturing device having the global shutter function is increasing. In the CMOS-type solid-state image-capturing device having the global shutter function, it is generally necessary to have a storage capacitance unit with a light shielding property in order to store signal charges generated by a photoelectric conversion unit until reading is performed. In this conventional CMOS-type solid-state image-capturing device, after all pixels are simultaneously exposed, signal charges generated by the photoelectric conversion units are simultaneously transferred from all of the pixels to storage capacitance units and temporarily stored in the storage capacitance units. Also, the signal charges are sequentially converted into pixel signals and read at a predetermined reading timing.
However, because the photoelectric conversion unit and the storage capacitance unit should be created on the same plane of the same substrate in the conventional CMOS-type solid-state image-capturing device having the global shutter function, an increase in a chip area is inevitable. Further, there is a problem in that the quality of a signal is deteriorated due to noise caused by light or noise caused by a leak current (dark current) occurring in the storage capacitance unit during a waiting period until signal charges stored in the storage capacitance unit are read.
In order to solve this problem, a method of preventing a chip area from increasing and preventing signal quality from deteriorating according to a structure in which a first substrate in which photoelectric conversion units are formed and a second substrate in which a plurality of MOS transistors are formed are bonded is disclosed in Japanese Unexamined Patent Application, First Publication No. 2012-248952.
However, when strong light has been incident on the solid-state image-capturing device, the reset level which is the reference potential changes to a level different from an ideal level due to the influence of light and a blackening phenomenon in which there is no difference between the signal level based on the signal charges stored in the photoelectric conversion unit and the reset level occurs. In order to solve this problem, suppressing the blackening phenomenon by providing a clip circuit for fixing the reset level in the solid-state image-capturing device having a structure in which two substrates are bonded is disclosed in Japanese Unexamined Patent Application, First Publication No. 2012-257037.